This invention relates to the field of static structures and, more specifically, to metallic structures anchored in prefabricated concrete panels or the like to facilitate lifting of such panels.
Prefabricated concrete panels and the like are commonly used in construction. Very often, such panels are sufficiently heavy that mechanical means, such as cranes, must be used to move them. For this reason, it is known to embed metallic anchors in prefabricated concrete panels or the like to facilitate the grasping and lifting of such panels.
Many prior art concrete anchors used bent rods or the like to secure the anchors in the concrete panels. Examples of such structures include those disclosed in U.S. Pat. Nos. 3,456,547; 3,596,971; 4,018,470; and 4,179,151. One drawback to such structures is that they are difficult to manufacture, requiring the welding of separate rods to build up the desires structures.
Other prior art concrete anchors, such as those proposed in U.S. Pat. Nos. 3,883,170 and 4,173,856, were formed from stamped or die-cut metal. Each of the anchoring elements proposed in these patents were split longitudinally through inner ends thereof so as to form oppositely-bent anchoring legs to help secure the anchoring elements in the concrete. The splitting of the anchoring elements and bending of the anchoring legs would have added steps to the processes required to manufacture these anchoring elements, thereby raising the cost of the elements"" manufacture.
Kelly U.S. Pat. No. 5,596,846; Kelly U.S. Design Pat. No. 392,752; and Kelly U.S. Design Pat. No. 389,251 proposed lifting anchors for embedment in concrete members. The lifting anchors comprised elongated bars having convergent and divergent surfaces wherein the divergent surfaces faced outwardly to direct axial pull-out forces imparted on the bars divergently and laterally into concrete members within which the anchors were embedded. The divergent surfaces terminated in enlarged feet formed at the proximal ends of the bars.
The lifting anchor proposed in Kelly U.S. Design Pat. No. 5,596,846 and of Kelly U.S. Design Pat. No. 389,251 also included a divergent wing extending laterally from an edge of the bar to transmit lateral lifting forces in outwardly divergent directions to a concrete member within which the bar was embedded. The addition of such a divergent wing would have required an additional welding step which would have increased the manufacturing cost of the lifting anchor.
Thus, there remains a need in the art for concrete anchors of relatively simple manufacture. There further remains a need in the art for combinations comprising such anchors embedded in concrete panels or the like sufficiently securely to resist pulling forces of magnitudes such as would be applied to the anchors while lifting or pivoting the panels.
These needs and others are addressed by an improved concrete anchor designed in accordance with the present invention for embedment in a concrete panel or the like, and by the structure formed by the combination of the concrete anchor with such a concrete panel. In accordance with a first embodiment, the preferred concrete anchor includes an elongated bar having substantially flat parallel faces, an inner end disposed within the panel, an outer end disposed within a recess in the surface of the concrete panel and side edges extending between the faces. The side edges extend in continuously diverging relationship from adjacent the outer end to adjacent the inner end.
The extension of the side edges in a continuously diverging relationship serves to firmly secure the concrete anchor in the concrete panel. More specifically, the configuration of the side edges of the preferred concrete anchor serves to direct the reaction forces generated by the application of a pulling force to the outer end of the elongated bar against the surrounding concrete of the concrete panel in a compressive mode. It is well known that concrete is strongest in compression. Thus, the extension of the side edges in a continuously diverging relationship serves to direct the reaction forces so as to maximize the ability of the surrounding concrete to sustain those reaction forces.
Preferably, the side edges of the preferred concrete anchor are substantially straight. Alternatively, the side edges include recesses defining recessed side edge sections in continuous diverging relationship.
The preferred concrete anchor further defines an elongated opening in its outer end and a void occupying a major portion of its inner end. Most preferably, the void is triangular or trapezoidal in shape so as to conform approximately to the continuously diverging relationship of the side edges. The void serves to further secure the concrete anchor in the concrete panel. When the concrete anchor is embedded in the concrete panel, as by casting the concrete panel over the concrete anchor, a xe2x80x9cnuggetxe2x80x9d of concrete forms through the void. This nugget acts as a detent to directly resist pulling forces applied to the outer end of the elongated bar. The nugget also reinforces the side edges so as to promote the action of the side edges in directing the reaction forces generated by the application of a pulling force on the outer end against the surrounding concrete in a compressive mode.
In accordance with a second embodiment, the preferred concrete anchor includes an elongated bar having substantially flat parallel faces; an inner end disposed within the panel; an outer end disposed within a recess in the surface of the concrete panel; and side edges, preferably substantially straight, which extend in a substantially parallel relationship between the faces. The outer end includes spaced, outwardly-projecting extensions disposed adjacent the side edges of the bar and, preferably, an elongated opening. The inner end is complementary in shape to the outer end, except that a major portion of the inner end is occupied by a void, preferably of triangular shape. As previously mentioned, when the concrete anchor is embedded in the concrete panel, as by casting the concrete panel over the concrete anchor, the void interacts with the concrete material to retain the concrete anchor in the panel.
Most preferably, the concrete anchor is formed from a single metal stamping. This allows for a particularly simple method of manufacture as compared with prior art concrete anchors.
Therefore, it is one object of the invention to provide a novel concrete anchor of relatively simple construction which, in combination with a concrete panel or the like, forms a durable structure capable of being pivoted or lifted by engagement of a crane or other suitable means with the concrete anchor. These and other objects, features and advantages of the present invention will be described in further detail in connection with preferred embodiments of the invention shown in the accompanying drawings.